Light Emitting Diodes (LEDs) have many advantages over conventional light sources, such as incandescent, halogen, and fluorescent lamps. These advantages include longer operating life, lower power consumption, and smaller size. Consequently, conventional light sources are increasingly being replaced with LEDs in traditional lighting applications. As an example, LEDs are currently being used in flashlights, camera flashes, traffic signal lights, automotive taillights and display devices.
Two prevalent types of LED form factors are surface-mount LEDs and thru-hole LEDs. Surface-mount LEDs are particularly well suited for applications that require a low device height whereas thru-hole LEDs are better suited for focusing/directing light (e.g., for narrow viewing angle applications). Smaller thru-hole LEDs and smaller surface-mount LEDs are generally desired to accommodate the public's desire to have smaller electronic devices.
As the light sources (e.g., LED dies) become smaller to achieve the economic cost advantage, several unwanted side-effects occur. Specifically, when the size of the LED die is reduced, but the overall light output of the LED die is maintained substantially constant, the current density for the LED die increases. This increased current density will lead to a higher heat density in the area proximate to the light-emitting surface of the LED die. Secondly, the increased current density will lead to a high photon density in the area proximate to the light-emitting surface of the LED die. Unfortunately, this increase in heat density and photon density can have deleterious effects on the materials that surround the light-emitting surface of the LED die. As an example, as the materials surrounding the LED die become degraded much more rapidly when subjected to increased heat and/or photon densities. Ultimately, the breakdown of material(s) surrounding the LED die will cause the overall light output of the illumination device to decrease.